The present invention is related generally to power management in a battery powered electronic system. More specifically, the present invention is related to a power management system that is employed by a portable electronic system by selectively placing various electronic sub-circuits within the portable electronic system into a sleep mode based on the battery voltage.
Many portable electrical devices utilize a rechargeable battery to provide power to the electrical devices. These devices include computers, cellular telephones, pagers, radios, power tools, and the like. For improved service life and extended time between charges, these batteries and devices often include a control circuit (commonly called a power controller, a battery control circuit, a charge controller, and the like) to control the charging and/or the discharging of the battery. The control circuit controls the battery charge by a charger circuit, and controls the discharge of the battery by deactivating control circuit units to prevent drainage of the battery unit.
A battery charge circuit having a given charge characteristic may be most appropriate for charging a battery based on various criteria such as battery type, and charge storage capacity. For example, Lithium-Ion batteries and Lithium-Polymer batteries are often used in portable applications such as cellular telephones. Lithium batteries are sensitive to excessive voltages, which may result in damage to the battery and/or a possibly explosive condition. The battery charger and controller design for a Lithium-Ion battery should include a suitable safety circuit (i.e., a shunt regulator) to prevent overcharging the battery.
The present invention is directed at a power management circuit for a battery operated electrical device that may include a number of switching circuits. The switching circuits are coupled between the battery and a corresponding one of various electronic sub-circuits. A battery monitoring circuit is arranged to monitor a voltage associated with the battery. Each switching circuit selectively couples a corresponding one of the electronic sub-circuits to the battery based on the battery voltage. In another example, the monitor circuit and the switching circuit functions are provided within the corresponding electronic sub-circuit. Battery power is conserved by selectively disabling (i.e., placing them in a sleep mode) the various electronic sub-circuits based on the battery voltage. The power management circuit may be arranged to select between charger circuits that have distinct charging characteristics, as well as to enable/disable various analog and digital electronics in the battery operated electrical device depending upon the monitored battery condition.